Moteur de recherche de fiches techniques de composants électroniques |
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TDA1220B Fiches technique(PDF) 7 Page - STMicroelectronics |
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TDA1220B Fiches technique(HTML) 7 Page - STMicroelectronics |
7 / 18 page APPLICATION INFORMATION (continued) FM Section IF Amplifier and limiter The 10.7 MHz IF signal from the ceramic filter is amplified and limited by a chain of four differential stages. Pin 16 is the amplifier input and has a typical input impedance of 6.5 KW in parallel with 14 pF at 10.7 MHz. Bias for the first stage is available at pin 14 and provides 100% DC feedback for stable operating conditions. Pin 15 is the second input to the amplifier and is decoupled to pin 14, which is grounded by a 20 nF capacitor. An RLC network is connected to the amplifier output and gives a 90 ° phase shift (at the IF centre frequency) between pins 13 and 12. The signal level at pin 13 is about 150 mV rms FM Detector The circuit uses a quadrature detector and the choise of component values is determined by the acceptable level of distortion at a given recovered audio level. With a double tuned network the linearity improves (distortion is reduced) and the phase shift can be optimized; however this leads to a reduction in the level of the recovered audio. A satisfactory compromise for most FM receiver applications is shown in the test circuit. Care shoul be taken with the physical layout. The main recommandations are: • Locate the phase shift coil as near as possible to pin 13. • Shunt pins 14 and 16 with a low value resistor (between 56Ω and 330Ω). • Ground the decoupling capacitor of pin 14 and the 10.7 MHz input filter at the same point. AM-FM Switching AM-FM switching is achieved by applying a DC voltage at pin 13, to switch the internal reference. Typical DC voltages (refer to the test circuit) Pins 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Unit AM 9 1.4 9 1.4 1.4 8.4 9 0.7 1.9 9 0 0.1 0.1 8.5 8.5 8.5 V FM 9 0.02 9 0.02 0.02 8.5 9 0 1.7 90998 88 V 7/18 TDA1220B |
Numéro de pièce similaire - TDA1220B |
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Description similaire - TDA1220B |
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